Hybrid vehicles may include both an internal combustion engine and an electric motor. In some hybrid configurations, either the internal combustion engine or the electric motor, either individually or in combination, may be used to provide the propulsive power for the vehicle. During certain situations, when the internal combustion engine is disengaged, it becomes necessary to automatically start the internal combustion engine, such as to provide additional propulsive power or for regenerating an energy storage device, e.g., a battery. These situations are commonly referred to as auto-starts.
For a typical hybrid auto-start, a hybrid system controller controls a rotational speed of the internal combustion engine to increase the rotational speed of the engine up to a desired engine speed, based on a calculated rotational engine speed profile, after which the engine is fueled and fired to start torque production. However, auto-starts may be combustion assisted, in which case the engine is fueled and fired as soon as the electric motor begins to spin the internal combustion engine, and before the internal combustion engine is rotating at the desired engine speed. During combustion assisted auto-starts, an engine controller uses a flare control algorithm to control the rotational speed of the engine. The flare control algorithm uses a single calibration table to define the desired engine speed of the internal combustion engine. Accordingly, during combustion assisted auto-starts, the hybrid system controller and the engine controller each define different values for the desired engine speed of the internal combustion engine, thereby creating inefficiency in the system.